The present invention relates to an apparatus and a method suitable for measuring the load sustained by an aircraft component. In particular, the present invention relates to an apparatus for determining the load sustained by an aircraft component when braking and/or manoeuvring the aircraft on the ground.
When an aircraft manoeuvres on the ground (including, for example, immediately after touch down), the aircraft is subjected to various loads including vertical wheel to ground loads and horizontal drag loads including, for example, loads caused by friction between the tyres of the wheels of the aircraft and the ground. The landing gear is subjected to significant horizontal loads on braking. The landing gear and other components of the aircraft have to be carefully designed in order for the aircraft to be able to withstand such loads, and other operational loads, but without unduly increasing the mass of the aircraft.
By using a load measuring device as part of a feedback braking system it is possible to limit, at least in part, the maximum load sustained by the airframe, landing gear, or a part thereof and/or to facilitate efficient braking of the wheels. In addition, such a load measuring device may be used to monitor and/or improve the fatigue life of an aircraft component. It may also be advantageous to use load measuring devices during the testing and development of new aircraft, for example, during a validation process. A load measuring device may also be used during normal mode analysis (NMA), for example during ground vibration tests or airborne tests.
It is known to use strain gauges as part of such load measuring devices. These, however, have disadvantages associated with them. For example, strain gauges may have to be bonded to the structure being monitored, may require specialist maintenance, may only be able to provide a local load measurement, may be easily damaged, may be susceptible to noise and/or may require temperature compensation. It is also known to use accelerometers, alongside strain gauges, in NMA. These have disadvantages associated with them, for example they may not be suitable for use on an aircraft in flight and may be costly to fit, and later remove, specifically for a ground vibration test.